MAke a dummy unit based off of chicken or footman or w/e, make it inable to move, attack, and give it shockwave, invulnerable (neutral) and locust. Then copy that and make one for each level of the spell you have. Name them like dummy 1 dummy 2 dummy 3 or w.e... then give them each a level of the ability in different abilities for each level.
Then for triggers do - unit casts spell
conditions spell = yourspellname
if level of yourspellhere for casting unit is equal to 1, then do
unit- create dummy unit level 1
order last created to orc tauren chieftan - shockwave
remove last created unit
unit- create dummy unit level 1
order last created to orc tauren chieftan - shockwave
remove last created unit
if level of yourspellhere for casting unit is equal to 2, then do
unit- create dummy unit level 2
order last created to orc tauren chieftan - shockwave
remove last created unit
unit- create dummy unit level 2
order last created to orc tauren chieftan - shockwave
remove last created unit
etc., do that for every level...
--donut3.5--